The incidence of theft from personal storage containers is on the rise. For example, the number of reported attacks on wall-mounted personal mail storage containers increased from 988 in 2000 to 2,819 in 2002.1 This increase in the number of thefts from wall-mounted personal storage containers highlights the need for improvements in the securing of personal storage lockers and delivered-goods lockers. This need for improvement also exists due to the potential for identity theft and loss of personal privacy, which result from theft in general. 1 Postal Service 39 CFR 111, Standards Governing the Design of Wall-Mounted Centralized Mail Receptacles, Final Rule.
Visual inspection, forensic analysis, and engineering testing measures of locks and storage containers have demonstrated that improvements in locks and storage containers could increase the security of items placed within the storage containers. With the rise in incidences of identity theft, improvements in security of personal information also becomes more important. As more and more goods are purchased through the Internet and shipped directly to a purchaser, securing of these delivered valuables becomes more important. Better equipment would improve the security of valuables and personal information within the storage container from theft.
Conventional methods of compromising and/or breaking into the storage containers are well documented. Methods include prying open the door of such containers with a flat head screw driver and gripping the cylinder collar of the locker lock with vise grips to remove the lock with torsion force.
A multitude of mechanical failures can occur upon application of a low cantilever load to the door of the storage container or upon the application of a low cantilever load to the lock itself. For example, fracture of the cam end of the lock plug may occur, causing the door to open. Other possible mechanical failures include fracture of the plug body and severing of the end of the cam from the plug. This latter mechanical failure also results in the door opening.
Similarly, compromising the security of the storage container via gripping the cylinder collar with vise grips and removing the lock with torsion force can lead to a multitude of mechanical failures. For example, under torsion, mechanical failures may include the loosening of the plug nut, which allows the cam to rotate more freely and the lock to open. The plug nut may also completely disengage from the bolt, resulting in the cam falling off the end of the plug. Because the cam engages the frame of the storage container or equivalent and prevents the door from opening, when the cam falls off the plug, the door readily opens.
Previous solutions to the problem of increasing the security of storage containers include the United States Postal Service (“USPS”) USPS-L-1172C version lock and associated locker system. The USPS-L-1172C lock can withstand a previously unachievable 1000-pound cantilever load requirement, an increase of 800% over earlier personal storage container locks. The USPS-L-1172C's plug design and cylinder could withstand the resultant forces of a 1000-pound cantilever load on a lock installed in a personal storage locker.2 This 1172C version lock also can withstand 1000-pound load applied to the cam, which is the part of the apparatus attached to the threaded end of the plug. 2The plug is the center rotating piece of a lock into which the key is inserted. The cylinder is the stationary piece of the lock that houses the plug and interfaces with the storage container door.
The 1172C meets the 1000-pound criteria with room to spare. Both the material and design contributed to the improved performance of the 1172C. The previous low-cost, but low-strength Zinc die-cast material for the plug was changed to a metal injection molded, precipitation hardened, stainless steel material. Manufacturing the plug in this way resulted in a 5/16 s thread of extreme strength on the plug without requiring any secondary machining processes. Additionally, manufacturing the plug this way had the additional advantage of being reasonably economical.
Design changes to meet the 1000-pound load criteria in the 1172C over previous versions included a locking plug nut. Because of this nut, the USPS-L-1172C could withstand aggressive torque load to its face without becoming loose or disassociated from the personal storage device. The USPS-L-1172C locking apparatus comprised a locking plug nut, which did not back off of the end of the plug bolt with vibration, cantilever load on the door of the storage container, or tensile load to the face of the cylinder.
Despite the great strength of the 1172C, increased strength and increased life may be warranted in locations known to have a high incidence of theft. Further, some environmental conditions require an increased resistance to corrosion. Changes in the existing lock apparatus are therefore desirable to meet higher break-in load criteria and increased corrosion resistance criteria.
The 1172C version of the plug specified a standard thread form that required a thread-locking style plug nut to provide adequate “grip” of any installed cam and also required a specialized version of one specific self-locking style nut that had been the only successful version to test out at load values exceeding the 1000-pound requirement. This superior strength performance came at a price of unexpected installation issues, however. In particular, the torque required to completely seat this self-locking nut exceeded, for most installers, the amount of torque that could be generated by previous standard installation methods and tools, for example a nut driver. Accordingly, it was sometimes necessary for installers to use a ratchet nut driver to properly install the prior art lock system. Thus, it is desirable to use a widely available standard nut as a plug nut, as opposed to the self-locking version used on the plug of the 1172C lock, enabling maintenance personnel to install a new lock with only a nut driver. It is further desirable to use less expensive plug nuts available in great numbers for convenience and cost efficiency.
Accordingly, it is desirable to provide a lock, locking method, and locking system that meets high load and corrosion resistance criteria. Moreover, it is desirable to provide a lock, a locking method, and a locking system that allows for installation of a new lock with only a nut driver. Finally, it is desirable to provide a lock, locking method, and locking system using widely available and cost-effective nuts.